ABSTRACT
This chapter examines the use of models to depict changes at the catchment scale in the context of geochemical processes, weathering and recharge in catchments. It examines the theme of how to couple hydrological, soil and weathering processes within a modelling perspective, to provide both a scientific and an applied goal. Computer simulation models increasingly have been relied upon to describe a variety of environmental impacts over the past few decades. These have ranged from limnological models relating nutrient input to eutrophication of freshwaters, to catchment models describing the impact of acid deposition on soil and surface water chemistry. The Plynlimon catchments experience rainfall with very variable chemistry while the streams exhibit a ‘flashy’ flow response to rainfall inputs. Therefore, one might expect large variations in stream water concentrations that mirror the rainfall signal.
